Volumetric liquid metering device

ABSTRACT

A volumetric liquid metering device has a meter chamber for receiving up to a predetermined volume of liquid, an inlet conduit for directing liquid into the meter chamber, a volumetric meter to indicate when the predetermined volume has entered, and a discharge conduit operable in response to a signal from the volumetric meter. The device can have a pair of coupled meter chambers, one b being filled as the other discharges. Valves control ingress and egress of liquid from the meter chambers, and alternate between chambers in response to a signal from the volumetric meter.

FIELD OF THE INVENTION

The present invention relates to a volumetric liquid metering devicethat affords an improvement over known devices for measuring volumes ofliquid, particularly for use in the dairy industry. The device is alsosuitable for measuring fruit juice and wine, or for measuring othercontinuous flow liquids such as water or petroleum.

BACKGROUND OF THE INVENTION

It has been found that electronic meters for the volumetric measurementof liquids, particularly milk, do not provide a sufficient degree ofaccuracy.

In the dairy industry it is a commonly accepted practice to allocate anamount of feed to an individual cow according to the volume of milkproduced by the individual cow. For example, high volume producing cowsreceive more grain whilst low volume producing cows receive less grain.Accordingly, accurate measurement of the volume of milk produced peranimal is required for the efficient and cost effective allocation ofgrain.

It is known to measure a volume of milk with a metering devicecomprising an electronic probe. Milk contains both butterfat and proteinwhich behave as electrolytes. Once a certain volume of milk isaccumulated in the meter, the butterfat and protein bridge an electricalcircuit, thus triggering a reading. If the concentration of protein andbutterfat in the milk remains constant then the accuracy of this methodof volumetric measurement is satisfactory. However, in practice theconcentration of butterfat and protein varies from cow to cow.Consequently, the volumetric measurement of milk with this particulardevice lacks consistent accuracy.

In contrast to the prior art, the present invention directly measuresthe volume of milk produced by the cow without relying on any othervariable or parameter associated with the milk or liquid. Accordingly,the device of the present invention consistently affords a greaterdegree of accuracy over other prior art devices and methods.

The metering chamber of existing metering devices is calibrated in afixed scale, for example, in liters. A further advantage of thevolumetric liquid metering device of the present invention is that theoperator has the option of being able to set the predetermined volume ofthe device and therefore is able to choose the unit of measurement ineither metric or imperial units.

Today cows are producing a greater volume of milk than in the past as aresult of improved genetics and better feeding techniques. Conventionalmethods of harvesting milk thus require increasingly larger diametermilk lines to collect the milk, which in turn need larger and morepowerful vane pumps.

In current milk harvesting situations, the same line is used for thesupply of vacuum to the milking plant and for the transport of milk tothe milk receival vessel. The use of one line for two different purposescan be problematic, especially when a cow or a group of cows releases asurge of milk, causing the milk line to become restricted by flooding.

Flooding of the line has the effect of reducing the amount of vacuumavailable upstream of the restriction, often causing an interruption ofvacuum supply to the upstream cows. The loss of vacuum supply upsets thecows by interrupting the milking routine and in extreme cases theupstream cow kicks off the cups.

To overcome this particular problem, the diameter of the milk line isincreased to avoid interruptions to the vacuum supply. Alternatively, asystem known as a loop line is installed. A loop line consists of twolines disposed parallel to one another and commonly connected at bothends to form a loop which allows the vacuum to be obtained from eitherside of the restriction caused by the high volume of milk.

The result of either increasing the diameter of the milk line orinstalling a loop line is the same. A greater demand is placed on thevane pump that supplies the vacuum. Accordingly, a large vane pump or aplurality of vane pumps is required with a consequent increase in energyconsumption.

By segregating the vacuum supply from the milk transporting line thereis a more uniform supply of vacuum for each cow and the milk lines donot have to be so large. It is therefore a further advantage of thepresent invention that when a plurality of volumetric liquid meteringdevices are used in a new milk harvesting situation the load on the vanepump is reduced, thus leading to energy savings.

The present invention has been designed so that it can also be installedin a dairy with conventional milk harvesting equipment such that onlyminor modifications to the system are required.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention there is provideda volumetric liquid metering device comprising a meter chamber forreceiving up to and including a predetermined volume of liquid, an inletconduit for directing liquid into the meter chamber, a volumetricmetering means to indicate when the predetermined volume of liquid hasentered the meter chamber, and a discharge conduit for dischargingliquid from the meter chamber in response to a signal from thevolumetric metering means.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

The invention will now be described, by example only, with reference tothe accompanying drawings in which:

FIG. 1 is a diagrammatic side elevation view of a volumetric liquidmetering device in accordance with the present invention;

FIG. 2 is a diagrammatic side elevation view of the volumetric liquidmetering device shown in FIG. 1 further comprising a means to muffleliquid turbulence caused by a sudden ingress of atmospheric air into thevolumetric liquid metering device;

FIG. 3 is a diagrammatic end elevation view of a pair of coupledvolumetric liquid metering devices as shown in FIG. 1;

FIG. 4 is a detailed schematic diagram of an internal valve mechanismused in the devices shown in FIGS. 1 to 3;

FIG. 5 is a schematic diagram of the pair of volumetric liquid meteringdevices shown in FIG. 3 coupled by the internal valve mechanism shown inFIG. 4;

FIG. 6 is a schematic diagram of a conventional milking system by whicha vacuum means harvests milk from a plurality of cows; and

FIG. 7 is a schematic diagram of the milking system shown in FIG. 6wherein a plurality of volumetric liquid metering devices in accordancewith the present invention are incorporated into the system.

Referring to FIG. 6 there is shown a conventional milking system 10. Thesystem 10 comprises a plurality of sets of cups 30, wherein each set ofcups 30 is provided with a respective first milk delivery line 32 and arespective first vacuum line 28, a second milk delivery line 34, asecond vacuum line 24 and a vane pump (not shown) which is commonlyknown as a vacuum pump.

Each first vacuum line 28 is endwise connected to the second vacuum line24. The vane pump provides a vacuum to the system 10 via the thirdvacuum line which is endwise connected to the second vacuum line 24. Itis common to locate an interceptor tank 14 between the second and thirdvacuum lines 24, 12 to prevent milk entering the vane pump via the thirdvacuum line 12. The second vacuum line 24 is also protected frominadvertent liquid suck back into the second vacuum line 24 by theinterceptor tank 14.

Each first vacuum line 28 is provided with a pulsator 26. The pulsator26 is a solenoid valve timed to open and close at predetermined periodscausing an alternating vacuum to be applied along the first vacuum line28 to the set of cups 30, thereby affording a pulsation effect on a partknown as inflations which are located inside a shell of the cups 30. Inthis way, the sucking action of a calf on the teat is mimicked and milkcan be extracted from the cow's udder.

The milk is then transferred along respective first milk delivery lines32 into the second milk delivery line 34 and thence into a receivalvessel 16. A centrifugal pump 20 transfers the milk stored in thereceival vessel 16 to a main storage tank via a third milk delivery line22. A vacuum is also commonly applied to the second milk delivery line34 through a fourth vacuum line 18 which interconnects the interceptortank 14 and the receival vessel 16.

It is envisaged that each set of cups 30 will be provided with arespective volumetric liquid metering device 1 as shown in FIGS. 1 to 5and 7, wherein each device 1 is arranged to receive and meter milkreceived from its respective first milk delivery line 32 before the milkis discharged into the second milk delivery line 34.

Referring to FIG. 1 there is shown the volumetric liquid metering device1. The volumetric liquid metering device 1 comprises a meter chamber 50for receiving up to and including a predetermined volume of liquid, ainlet conduit 46 for directing liquid into the meter chamber 50, avacuum conduit 40 for applying a vacuum to the meter chamber 50 in orderto draw liquid into the meter chamber 50 via the inlet conduit 46, avolumetric metering means to indicate when the predetermined volume ofliquid has entered the meter chamber 50, and a discharge conduit 64 fordischarging liquid from the meter chamber 50 into the second milkdelivery line 34 in response to a signal from the volumetric meteringmeans.

The meter chamber 50 is either cylindrical or rectangular in shape,whichever is appropriate to best suit space constraints of the operatingenvironment and the type of liquid which is to be measured.

For convenience, the meter chamber 50 is provided with a viewing panel(not shown) which allows an operator to visually monitor the performanceof the device 1. It is envisaged that the viewing panel could comprise amajor portion of the meter chamber 50.

The inlet conduit 46 is in fluid communication with a liquid supplyconduit 48. The liquid supply conduit 48 is in fluid communication withthe first milk delivery line 32. The inlet conduit 46 extends into aninterior of the meter chamber 50 to direct liquid flowing from the firstmilk delivery line 32 into the meter chamber 50 for volumetricmeasurement. Ingress of liquid through the inlet conduit 46 and into themeter chamber 50 is controlled by a valve mechanism 3 shown in greaterdetail in FIG. 4. The valve mechanism 3 corresponding to the liquidsupply conduit 48 is housed in a valve housing 44.

The vacuum conduit 40 is in fluid communication with the second vacuumline 24 so as to apply a vacuum to the meter chamber 50 in order to drawliquid into the meter chamber 50 via the inlet conduit 46. Applicationof vacuum through the vacuum conduit 40 is controlled by the valvemechanism 3 shown in greater detail in FIG. 4. The valve mechanism 3corresponding to the vacuum conduit 40 is housed in valve housing 44.

The discharge conduit 64 is in fluid communication with the second milkdelivery line 34. The discharge conduit 64 is arranged to dischargeliquid from the meter chamber 50 into the second milk delivery line 34when the meter chamber 50 is filled to its predetermined volume. Egressof liquid through the discharge conduit 64 and into the second milkdelivery line 34 is controlled by a valve mechanism 3 shown in greaterdetail in FIG. 4. The valve mechanism 3 corresponding to the dischargeconduit 64 is housed in a valve housing 44.

The volumetric metering means comprises a device which transmits asignal in response to detection of a predetermined volume of liquid inthe meter chamber 50. For example, the volumetric metering means maycomprise a laser beam disposed at a particular location in the meterchamber 50, to correspond with a predetermined volume of liquid, whereina signal is emitted by the device when a rising liquid level in themeter chamber breaches the laser beam. Alternatively, the device maycomprise a probe to detect the liquid, wherein the probe is disposed inthe meter chamber 50 at a location corresponding with a predeterminedvolume of liquid, wherein a signal is omitted by the probe when itdetects the liquid.

Preferably, the volumetric metering means comprises a float switch 58fixed hingedly to a side wall of the meter chamber 50. The float switchis movable between a first position (represented in phantom) wherein themeter chamber 50 is empty, and a second position (represented in solidline) wherein the meter chamber 50 is filled to its predeterminedvolume. The ingress of liquid into the meter chamber 50 causes the floatswitch 58 to rise from the first position to the second position. Whenthe float switch 58 is in the second position, an electrical circuit iscaused to close, thus triggering a signal to activate the respectivevalve mechanisms 3 operating the inlet conduit 46, vacuum conduit 40,and discharge conduit 64, such that the further ingress of liquid intothe meter chamber 50 through the inlet conduit 46 and vacuum applied tothe meter chamber 50 via the vacuum inlet 40 are halted, and thepredetermined volume of liquid received in the meter chamber 50 isdischarged into the second milk delivery line 34 through the dischargeconduit 64.

Where it is desired to volumetrically meter continuous flow liquids,such as fruit juice or wine, the device 1 is arranged such that thefloat switch 58 is fixed to an arm 60 by a hinged mechanism 61. The arm60 depends downwardly into the interior of the meter chamber 50 throughan aperture disposed in an upper wall of the meter chamber 50. The arm60 is threaded through a compression nut 62 contiguously disposed on anexterior of the upper wall of the meter chamber 50. When the compressionnut 62 is loosened the arm 60 can be slidably moved in an upward ordownward direction such that the float switch 58 is located in an upperor lower portion of the interior of the meter chamber 50, accordingly.In this way the predetermined volume of the device 1 at which the floatswitch 58 is in the second position can be altered. Retightening thecompression nut 62 ensures that atmospheric air cannot enter the meterchamber 50.

It is envisaged that the liquid supply conduit 48 would be provided witha probe and a timing means, wherein the probe and the timing means arearranged to transmit a signal to deactivate the volumetric meteringmeans after no liquid has been sensed for a predetermined period of timein the liquid supply conduit 48. The signal would cause a commercialvacuum solenoid valve, located between the second vacuum line 24 and thevacuum conduit 40, to close thus shutting off vacuum supply to the meterchamber 50. Additionally, or alternatively, the pulsator 28 could bedeactivated in response to the signal. In this way, the volumetricliquid metering device 1 can be isolated from the second vacuum line 24.

An upper portion of the meter chamber 50 is provided with a plurality oflaterally extending baffle plates 54. Each baffle plate 54 is perforatedwith randomly spaced apertures. The apertures are arranged in astaggered configuration to encourage vacuum flow in the meter chamber 50in an indirect line to the second vacuum line 24. In this way, it isenvisaged that the potential for egress of liquid received in the meterchamber 50 into the second vacuum line 24, resulting from disturbance ofliquid received in the meter chamber 50 by turbulence or steam, will beminimal.

When the cow kicks the milking cups 30 off its teats there is a suddeningress of atmospheric air into the meter chamber 50 which is undervacuum when the device 1 is in use. The sudden ingress of air has anexplosive or turbulent effect on the liquid already received in themeter chamber 50, causing the float switch 58 to act in an erraticmanner between the first and second position, thereby resulting in amalfunction of the meter. Incorporation of a means to muffle liquidturbulence caused by a sudden ingress of atmospheric air into themetering chamber to minimise and absorb some of the kinetic force of thesudden ingress largely overcomes the abovementioned problem.

Preferably, the meter chamber 50 is further provided with a means tomuffle liquid turbulence caused by a sudden ingress of atmospheric airinto the volumetric liquid metering device 1, as shown in FIG. 2. Themeans to muffle liquid turbulence caused by a sudden ingress ofatmospheric air into the volumetric liquid metering device comprises ablast chamber 55.

The blast chamber 55 is a box-like housing constructed around the inletconduit 46 proximal to the baffle plates 54. The blast chamber 55 isprovided with an appropriately sized opening to discharge fluid into alower portion of the metering chamber 50. In the event of the cups 30being kicked off by the cow, the blast chamber 55 has the effect ofreducing the explosive effect caused by the rapid loss of vacuum causedby the introduction of atmospheric air into the meter chamber 50. Theopening of the blast chamber 55 is configured with an appropriatelydesigned bend 67 as shown by a dotted line in FIG. 2.

A downwardly inclined surge plate 59 is fixed by mounting straps 57 toan underside of the blast chamber 55. The surge plate 59 has the effectof segregating the meter chamber 50 into an upper compartment and alower compartment so that the introduced atmospheric air which causesthe blast effect is directed to the upper compartment and thence to thesecond vacuum line 24 via the vacuum conduit 40.

As milk is discharged from the blast chamber 55 it falls onto thedownwardly inclined surge plate 59 and runs down to an end of the surgeplate 59 where it is directed to the lower compartment of the meterchamber 50 which houses the float switch 58. Affixed to an exterior ofthe blast chamber 55 is a splatter plate 61, which reduces the incidenceof liquid being pulled into the baffle plates 54 from the blast chamber55. The abovementioned means allows for a smoother transition of thefloat switch 58 from the first position to the second position, andminimises the deviation of the float switch 58 due to pressurefluctuations when the float switch 58 is midway between the first andsecond positions.

It will be understood that the float switch 58 will be located in theinterior of the meter chamber 50 such that when the float switch 58 isin the second position no liquid will be allowed to get above a givenpoint in the meter chamber 50 and in so doing pass between the baffleplates and enter the second vacuum line 24 via the vacuum conduit 40.

Referring to FIGS. 3, 4, and 5, it is preferable that the volumetricliquid metering device 1 comprises a first meter chamber 50 a and asecond meter chamber 50 b, including respective inlet conduits 46 a and46 b, wherein the first and second meter chambers 50 a, 50 b are coupledtogether via a plurality of valve mechanisms 3.

The vacuum supply pipe 40 is endwise connected to a hollow T-shapedmember 42 and a pair of valve housings 44. In this way, the first andsecond meter chambers 50 a, 50 b are both supplied with a vacuum bycommon vacuum supply pipe 40.

The liquid supply conduit 48 is endwise connected to its respectivehollow T-shaped member 42 and pair of valve housings 44. In this way,respective inlet conduits 46 a, 46 b of the first and second meterchambers 50 a, 50 b are both supplied with liquid by common liquidsupply conduit 48.

The discharge conduit 64 is endwise connected to a hollow T-shapedmember 66 and respective pair of valve housings 44. In this way, liquidis discharged from the first and second meter chambers 50 a, 50 b viacommon discharge conduit 64.

The valve housings 44 house a plurality of valve mechanisms 3 as shownin FIG. 4. The plurality of valve mechanisms 3 refers to a set ofvalves, preferably three in number, which control switching between thefirst and second meter chambers 50 a, 50 b. Changing the position of theplurality of valving mechanisms 3 allows vacuum to be appliedalternately between the first meter chamber 50 a and the second meterchamber 50 b.

For example, when vacuum is applied to the first meter chamber 50 a todraw liquid through the liquid supply conduit 48 and the inlet conduit46 a, the valve mechanism 3 opens the first meter chamber 50 a whilstclosing off the second meter chamber 50 b to any ingress of liquidthrough the liquid supply conduit 48 and the inlet conduit 46 b.

Further, the plurality of valve mechanisms 3 are arranged such that whena meter chamber 50 is closed to vacuum, the valve mechanism 3 opens themeter chamber 50 to allow the predetermined volume of liquid containedtherein to be discharged through the discharge conduit 64. Thus, tofollow the abovementioned example, when the second meter chamber 50 b isclosed to vacuum, the valve mechanism 3 allows the second meter chamber50 b to be drained of its predetermined volume of liquid through thedischarge conduit 64. In this way, whilst one meter chamber 50 isfilling, the other meter chamber 50 coupled thereto is draining.

When the float switch 58 reaches the second position in the first meterchamber 50 a, in other words, the predetermined volume of liquid hasentered the first meter chamber 50 a, the plurality of valve mechanisms3 change position, in response to a signal from the float switch 58, toallow the second meter chamber 50 b to be filled whilst the first meterchamber 50 a empties.

It is envisaged that, in practice, the plurality of valve mechanisms 3will continue to alternate between first and second meter chambers 50 a,50 b until the cow has completed milking.

FIG. 4 shows the internal workings of the valve mechanism 3 which iscommon to all three valve mechanisms adjoined to the first and secondmeter chambers 50 a and 50 b as shown in FIG. 3.

A diaphragm casing 80 is of a split construction and held together by asuitable fastening means 82. The fastening means 82 also retains adiaphragm 84 in a fixed position within the diaphragm casing 80.

The diaphragm 84 is centrally held between a flat washer 86 and aretaining nut 88 which is fixed to a drive shaft 90. The drive shaft 90is a common shaft running between two diaphragm casings 80 that areaffixed either side of the first and second meter chambers 50 a and 50b.

A suitable wiper seal, commonly found in pneumatics and hydraulics, isinstalled between the wall of the valve housing 44 and the diaphragmcasing 80 to restrict access of liquid or air into the diaphragm casing80.

The valve housing 44 has a suitable hole through one side to enable thedrive shaft 90 to slide to the left or to the right. On the drive shaft90 a suitable bucket seal 94 is held between a retaining washer 96 and abucket housing 98 which is suitably fixed to the drive shaft 90.

This same configuration is repeated in the valve housing 44 affixed tothe second meter chamber 50 b but with the bucket seal 94 and the buckethousing 98 facing each other to enable the opening and closing of thefirst and second meter chambers 50 a, 50 b.

The solid lines show that the shaft has been forced over to the extremeleft of FIG. 4 causing the right hand bucket seal 94 to come in contactwith the wall of the valve housing 44 and the bucket seal 94 to flareout against the wall of the valve housing 44 thus blocking off entry tothe second meter chamber 50 b.

The bucket seal 94 in the solid line configuration has returned to itsnatural state in the valve housing 44 affixed to the first meter chamber50 a allowing for the entry of the vacuum means and/or the entry ordischarge of the milk. The dotted line indicates the drive shaft 90 withthe bucket housing 98, the bucket 94 and the retaining washer in itsalternate configuration in which the first meter chamber 50 a is closed.

There are provided first and second compressed air lines 100, 101,wherein first and second lines 100, 101 are the means to facilitate thereciprocal motion of the drive shaft 90 within the valve mechanism 3. Acompressed air control solenoid valve for actuating the first and secondcompressed air lines 100, 101 in alternate order is also provided,wherein the compressed air control solenoid valve is arranged to actuatethe first and second compressed air lines 100, 101 in response to asignal received from the float switch 58 of the first meter chamber 50 aor the second meter chamber 50 b when the float switch 58 is in thesecond position. When the appropriate signal is received from the floatswitch 58, compressed air is directed on to the diaphragm 84 causing thedrive shaft 90 to move reciprocally within the valve mechanism 3 andthus open the first meter chamber 50 a and close the second meterchamber 50 b, or vice versa.

In other words, the transmission of the signal from the float switch 58to the compressed air solenoid control valve will cause the plurality ofvalve mechanisms 3 to switch from one meter chamber 50 to the othercoupled meter chamber 50 by acting upon the appropriate diaphragm in theplurality of valve mechanisms 3 as shown in FIG. 4.

FIG. 5 shows the first and second meter chambers 50 a and 50 b connectedwith the valve mechanisms 3 and the respective diaphragm casings 80. Thevalve mechanism 3 corresponding to the vacuum conduit 40 is shown inexploded view in relation to the first and second meter chambers 50 aand 50 b in order to clarify the working interrelationship between thefirst and second compressed air lines 100, 101 and the first and secondmeter chambers 50 a and 50 b.

Referring to FIG. 5, the black solid line represents a flow ofcompressed air via the first compressed air line 100 to three diaphragmcasings 80 thus causing the respective drive shafts 90 (see FIG. 4) tomove reciprocally within the valve mechanism 3. Air fills a voidcontaining the diaphragm 84 and the casing 80 thus pushing the driveshaft 90 with the bucket seal 94 to the appropriate position.

In this particular example, the drive shafts 90 are pushed into aposition to allow the second meter chamber 50 b to be filled via theliquid supply conduit 48 and the inlet conduit 46 b whilst thepredetermined volume of liquid received in the first meter chamber 50 ais discharged via the discharge conduit 64.

When the predetermined volume of liquid has entered the second meterchamber 50 b, the respective float switch 58 rises to the secondposition and transmits a signal to the compressed air control solenoidvalve. The compressed air control solenoid valve responds to the signalby actuating the second compressed air line 101 (shown in dottedoutline).

In this way, the position of the plurality of valve mechanisms 3 isreversed to allow the first meter chamber 50 a to commence filling viathe fluid supply conduit 48 whilst the second meter chamber 50 bcommences discharging via the discharge conduit 64.

The third compressed air line 102 is connected to the second meterchamber 50 b. A connection between the third compressed air line 102 andthe second meter chamber 50 b is opened when the second meter chamber 50b is discharging in order to break the retained vacuum in the secondmeter chamber 50 b. In this way, faster discharge of liquid through thedischarge conduit 64 is encouraged under positive pressure.

The fourth compressed air line 103 is connected to the first meterchamber 50 a. A connection between the fourth compressed air line 103and the first meter chamber 50 a is opened when the first meter chamber50 a is discharging in order to break the retained vacuum in the firstmeter chamber 50 a. In this way, faster discharge of liquid through thedischarge conduit 64 is encouraged under positive pressure.

The valve housing 44 has an appropriate means for internal inspectionthrough the cover 68 with a suitable gasket that is installed betweenthe valve housing 44 and the cover 68 and retained by suitable fasteningmeans 70.

The diaphragm casing 80 (see FIG. 4) is retained within a flange 72 andis fixed to the valve housing 44.

In FIG. 7 a plurality of volumetric liquid metering devices 1 areinstalled and piped as shown such that the vacuum supply can only beobtained from the second vacuum line 24.

The first milk delivery line 32 from the cups 30 is attached to thevolumetric liquid metering device 1 via a liquid supply conduit 48 (SeeFIG. 1). The volumetric liquid metering device 1 is connected to thesecond milk delivery line 34 which transports the milk via the pump 20through the third milk delivery line 22 to the main storage tank.

An additional commercial moisture trap 36 may be installed on the secondvacuum line 24 to prevent any chance of moisture being transmitted tothe vacuum pump. A suitable blocking means 38 is located between thereceival vessel 16 and the second milk delivery line 34 in order toreduce the load on the vacuum pump by removing the receival vessel 16and the second milk delivery line 34 from the vacuum circuit.

The layout of piping, as described above with reference to FIG. 7, leadsto substantial energy savings. Currently, all known types of milk meterare installed on the first milk delivery line 32 and flow into thesecond milk delivery line 34.

It is envisaged that electronic circuitry would be installed to controlthe metering device and to record various information. For instance,because a cow lets down milk more quickly in the early stages of milkingand more slowly in the later stages of milking the ability to vary thespeed of the pulsation rate will be included in the electronic controloptions. In this way the pulsing action can be adjusted to be faster orslower so that the cow can be milked out more efficiently with a view toreducing the total milking time.

It is preferred that the devices 1 would be installed in an exactlyvertical position however it is recognised that owing to dairy designthis is not always possible and a few degrees either side of vertical isacceptable.

The mechanical means of metering the amount of liquid using the twometering chambers has been described. This amount of milk would berecorded using the electrical pulses that the float switch 58 transmits.

The preferred option will be for the capacity of each meter chamber 50to be set to a predetermined volume prior to installation, thenaccurately recorded when installed by weighing the contents of eachchamber 50 of the device 1 and transferring this data to a personalcomputer in order to record the individual capacities of each chamber ofeach device 1 installed.

Using standard computing techniques a running tally on each individualdevice would be logged by combining the gross volume of the first meterchamber 50 a with the gross volume of the second meter chamber 50 b. Thetotal amount recorded for the device 1 would be displayed via a LCD orsimilar suitable visual display.

The dairy farmer needs the individual total for each cow and these wouldbe transferred to a personal computer that will also keep a runningtally of individual totals to provide a herd total for each milking.

This method of calibration has the advantage of reducing the necessityfor sealing mechanisms and 0 rings that are prone to breakdown.

To record this information a keypad, preferably with visual display,would be designated for each volumetric liquid meter device 1 within agiven dairy to enable entry of the cow's identification number and torecord the volume of harvested milk in order for the data to betransferred to a personal computer or microprocessor.

A plurality of volumetric liquid metering devices 1 would be used in amilk harvesting system so that the milk production of all cows could bemeasured.

Whilst this invention has been described for measuring a pulsating flowof liquid as is required for the milk harvesting industry, it isintended that it can also be used for measuring continuous flow liquidsas would be required for measuring or bottling liquids such as juices orwine. With continuous flow liquids the operator will set the requiredvolume of the metering chamber using suitable commercial measuringapparatus. For measuring continuous flow liquids the vane pump could bereplaced by a centrifugal pump and the volumetric liquid metering device1 would merely require the valve mechanisms 3 relating to liquid inletand liquid discharge, as the valve mechanism 3 required for controllingthe vacuum supply is specific to milk harvesting.

The accurate measurement of petroleum is impeded by the presence of lowmolecular weight components, particularly methane, which tend to causefrothiness in the petroleum liquid. It is also envisaged that thevolumetric liquid metering device 1 could be successfully adapted tomeasure petroleum. The device 1 is already arranged to apply a vacuum tothe meter chamber 50 such that any volatile low molecular weightcomponents could be separated from the petroleum liquid, thus reducingfrothing. The device 1 could also be adapted such that a positivepressure could be applied to the meter chamber 50 to assist thedischarge of low viscosity petroleum from the meter chamber 50.

Modifications and variations such as would be apparent to the skilledaddressee are considered within the scope of the present invention.

What is claimed is:
 1. A volumetric liquid metering device formeasurement of continuous flow liquids comprising first and second meterchambers wherein each meter chamber is arranged to receive up to andincluding a predetermined volume of liquid; each meter chamber beingprovided with: an inlet conduit for directing liquid into the meterchamber wherein the ingress of liquid through the inlet conduit and intothe meter chamber is controlled by a first valve mechanism; a means toapply negative pressure to the meter chamber to draw liquid into themeter chamber via the inlet conduit; a volumetric metering means toindicate when the predetermined volume of liquid has entered the meterchamber; a discharge conduit for discharging liquid from the meterchamber wherein the discharge of liquid from the meter chamber throughthe discharge conduit is controlled by a second valve mechanism, thefirst and second valve mechanisms being actuated in response to a signalfrom the volumetric metering means; and a means to apply positivepressure to the meter chamber to encourage discharge of liquid from themeter chamber via the discharge conduit; wherein the first meter chamberis coupled to the second meter chamber via the first and second valvemechanisms, the first and second valve mechanisms being configured suchthat liquid is received in the second meter chamber when liquid isdischarged from the first meter chamber, and vice versa.
 2. Thevolumetric liquid metering device according to claim 1, characterised inthat the meter chamber comprises a means to muffle liquid turbulencecaused by a sudden ingress of atmospheric air into the volumetric liquidmetering device.
 3. The volumetric liquid metering device according toclaim 1 or claim 2, characterised in that the volumetric metering meanscomprises a float switch movable between a first position, wherein themeter chamber is empty, and a second position, wherein the predeterminedvolume of liquid is received in the meter chamber, the float switchbeing arranged, in use, to transmit a signal when the float switch is inthe second position.
 4. The volumetric liquid metering device accordingto claim 3, characterised in that the predetermined volume of liquidreceived in the meter chamber can be adjusted by relocating the secondposition of the float switch.
 5. The volumetric liquid metering deviceaccording to claim 1, characterised in that the means to apply negativepressure to the meter chamber comprises a vacuum conduit interconnectinga vacuum supply and the meter chamber.
 6. The volumetric liquid meteringdevice according to claim 1, characterised in that the means to applypositive pressure to the meter chamber comprises a source of compressedair interconnected to the meter chamber.
 7. The volumetric liquidmetering device according to claim 1, characterised in that the meterchamber is provided with a viewing panel.
 8. The volumetric liquidmetering device according to claim 1, characterised in that the deviceis provided with a probe and a timing means, wherein the probe and thetiming means are arranged to transmit a signal to deactivate thevolumetric metering means after no liquid has been sensed for apredetermined period of time in the inlet conduit.
 9. The volumetricliquid metering device according to claim 1, characterised in that anupper portion of the meter chamber is provided with a plurality oflaterally extending baffle plates.
 10. The volumetric liquid meteringdevice according to claim 9, characterised in that the baffle plates areperforated with randomly spaced apertures.
 11. The volumetric liquidmetering device according to claim 10, characterised in that theapertures are arranged in a staggered configuration.
 12. The volumetricliquid metering device according to claim 1, characterised in that ismuffled by liquid turbulence caused by a sudden ingress of atmosphericair into the volumetric liquid metering device comprises a blastchamber.
 13. The volumetric liquid metering device according to claim12, characterised in that the blast chamber is a box-like housingconstructed around the inlet conduit, wherein the housing is providedwith an opening to discharge fluid into a lower portion of the meterchamber.
 14. The volumetric liquid metering device according to claim 12or claim 13, characterised in that the blast chamber is provided with adownwardly inclined plate fixed to an underside of the blast chamber,wherein the plate segregates the meter chamber into an upper compartmentand a lower compartment so that the sudden ingress of atmospheric air isdirected to the upper compartment and received liquid is directed to thelower compartment.
 15. The volumetric liquid metering device accordingto any one of claims 1 to 14, characterised in that the first and secondvalve mechanisms are caused to switch between the first meter chamberand the second meter chamber, and vice versa, in response to the signalfrom the volumetric metering means of respective first and second meterchambers.